Acknowledgment-based flexible fec selection

ABSTRACT

An optical network unit (ONU) includes a transmitter and receiver to optically communicate with an optical line terminal (OLT) of a passive optical network. The ONU is configured to send an acknowledgment message to the OLT in response to a burst-profile message unicast by the OLT. The acknowledgement message indicates unsupported forward error correction (FEC) code in response to the burst-profile message identifying an FEC code for upstream transmission and the ONU not supporting the FEC code for upstream transmission to the OLT.

BACKGROUND Field of the Disclosure

The present disclosure relates to communications systems and, morespecifically, to passive optical networks that employ forward errorcorrection encoding.

Description of the Related Art

This section introduces aspects that may help facilitate a betterunderstanding of the disclosure. Accordingly, the statements of thissection are to be read in this light and are not to be understood asadmissions about what is prior art or what is not prior art.

Forward error correction (FEC) may be used to support improvedcommunications over passive optical networks (PONs).

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure will become more fully apparent from thefollowing detailed description, the appended claims, and theaccompanying drawings in which like reference numerals identify similaror identical elements.

FIG. 1 is a block diagram of a PON network;

FIG. 2 is a flow diagram of the processing implemented by the OLT ofFIG. 1 to determine whether a particular ONUk supports a specified burstprofile have an identified FEC code j, according to certain embodimentsof the disclosure;

FIG. 3 is a flow diagram of the processing implemented at the ONUk ofFIG. 2, in response to the receipt of the PLOAMd burst-profile messagefrom the OLT, according to certain embodiments of this disclosure;

FIG. 4 schematically illustrates an example of the OLT of FIG. 1; and

FIG. 5 schematically illustrates an example of an ONU of FIG. 1.

DETAILED DESCRIPTION

Detailed illustrative embodiments of the present disclosure aredisclosed herein. However, specific structural and functional detailsdisclosed herein are merely representative for purposes of describingexample embodiments of the present disclosure. The present disclosuremay be embodied in many alternate forms and should not be construed aslimited to only the embodiments set forth herein. Further, theterminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments of the disclosure.

As used herein, the singular forms “a,” “an,” and “the,” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It further will be understood that the terms “comprises,”“comprising,” “contains,” “containing,” “includes,” and/or “including,”specify the presence of stated features, steps, or components, but donot preclude the presence or addition of one or more other features,steps, or components. It also should be noted that in some alternativeimplementations, the functions/acts noted may occur out of the ordernoted in the figures. For example, two figures shown in succession mayin fact be executed substantially concurrently or may sometimes beexecuted in the reverse order, depending upon the functions/actsinvolved.

The 10-Gigabit-capable Symmetric Passive Optical Network (XGS-PON)Standard, ITU-T G.9807.1, Amendment 1, the teachings of which areincorporated herein by reference in their entirety, specifiesrequirements for conforming PON networks. According to the XGS- PONStandard, transmissions are (optionally) encoded using the same,pre-defined Reed-Solomon (RS) FEC code, in which outgoing data isencoded to provide redundant information that can be used by therecipient to detect and correct certain bit errors that can occur duringtransmission.

U.S. Provisional Patent Application No. 63/092,473, dated 10 Oct. 2020,the teachings of which are incorporated herein by reference in theirentirety, provides implementation details about FEC coding in generaland LDPC coding in particular.

Herein, various embodiments provide messaging structures and protocolsto enable flexibility in upstream FEC coding. Such FEC codingflexibility may be useful, e.g., because lasers of optical network units(ONUs) are typically low cost and have variable quality. Also, thequality of transmissions may be limited by temperature variations and/orthe distance of the ONU from the optical line terminal (OLT). Messagingstructures of PON systems typically are limited by overhead constraintsand implemented by standards. In light of these potential difficulties,various embodiments provide messaging structures to support flexibilityin upstream FEC coding and also enable evolution of such flexibility,e.g., as a PON grows and/or evolves.

FIG. 1 is a block diagram of a PON network 100. The PON network 100 hasa point-to-multi-point (P2MP) topology that includes an optical lineterminal (OLT) 102 that transmits downstream optical signals to andreceives upstream optical signals from a number of different opticalnetwork units (ONUs) 106 over an optical fiber plant 104 that containsoptical fibers and splitters/combiners, but typically does not haveactive components. The optical fiber plant 104 is typically a passiveoptical distribution network with a tree-like architecture. The PONnetwork 100 employs time-division multiplexing (TDM) in which each ONU106 of the same upstream transmission wavelength may transmit upstreamto the OLT 102 in a corresponding time window so that different ones ofthe ONUs 106 do not transmit upstream, on the same wavelength channel,in the same time window. Some PON networks conform to standards, such asthe ITU G.989.3 (NG-PON2) Standard, that employ time- andwavelength-division multiplexing (TWDM) in which ONUs may transmitupstream signals using different wavelengths. Various PON networks relyon the ONUs being able to operate in a burst mode, in which an ONUtransmits bursts of uplink signals during allocated time windows, duringwhich only one ONU transmits at a given time for a particular wavelengthchannel.

In various embodiments, the PON network 100 typically supports abi-directional messaging system between the OLT 102 and the ONUs 106,e.g., to support TDM operation. The messaging system will typicallyenable the OLT 102 to identify individual ONUs 106 and assign theretotime windows for optically transmitting upstream to the OLT 102, i.e.,on a particular wavelength channel. The messaging system may also enablethe OLT 102 to learn various characteristics of individual ones of theONUs 106 and to assign thereto operating parameters for upstream opticaltransmissions.

In certain embodiments, such a messaging structure may be supported byphysical-layer operation, administration, and management (PLOAM)messages. The OLT 102 may transmit downstream PLOAM messages, i.e.,PLOAMd messages, to the ONUs 106 via the optical fiber plant 104, andthe ONUs 106 may transmit upstream PLOAM messages, i.e., PLOAMumessages, to the OLT 102 via the fiber plant 104, e.g., in response tothe PLOAMd messages or as requested by the OLT 102.

In one possible state of operation of the PON network 100, the OLT 102operates in a continuous mode, in which the OLT 102 may continuouslytransmit signals to the ONUs 106, where those signals may include one ormore unicast PLOAMd messages to one or more of the ONUs 106. A unicastPLOAMd message is a message transmitted from the OLT 102 to a specifiedONU 106. Note that the fiber plant 104 passively broadcasts downstreamsignals from the OLT 102 to all ONUs 106, including unicast PLOAMdmessages. While a unicast PLOAMd message may be received by each ONU106, such a message contains information that identifies only a singleONU 106 as the intended recipient of the unicast PLOAMd message. EachONU 106 may process such a unicast PLOAMd message to determine whetheror not it is the intended recipient. If it is the intended recipient,that ONU 106 will continue to process that PLOAMd message appropriately,while other ONUs 106 will typically ignore the PLOAMd message afterdetermining that they are not the intended recipient.

In the PON network 100, the OLT 102 may encode its downstream datasignals using a pre-defined default FEC code, e.g., based on LPDC codingor RS coding. An FEC code is used to correct errors introduced duringthe communication of data. An FEC code can be used to, e.g., encode aset of data bits into a data codeword consisting of the data bits and aset of additionally generated parity bits, e.g., for use in encoding anupstream burst transmission. At the receiver, the FEC code can be usedto decode the data codewords and correct any errors introduced duringthe communication, thus obtaining the error-free data bits. In variousembodiments herein, one or more of the ONUs 106 of FIG. 1 may beindividually and independently capable of transmitting upstream datasignals to the OLT 102 using any one of two or more differentpre-defined FEC codes, e.g., based on LDPC coding or RS coding. In someimplementations, the two or more pre-defined FEC codes may include thesame pre-defined default FEC code used by the OLT 120 and one or morepre-defined alternative (i.e., non-default) FEC codes. The OLT 102 knowswhat the pre-defined FEC codes are, but, other than the default FECcode, the OLT 102 does not have a priori knowledge of the one or morenon-default FEC codes that may be individually and independentlysupported by the different ONUs 106.

In certain implementations of the present disclosure, each different FECcode is uniquely identified by (i) a baseline LDPC code, which is usedfor at least the majority of a burst, and (ii) possibly one or moreburst-terminating LDPC codes for efficiency improvement of the lastcodeword in the burst. Each different LDPC code may be based ondifferent puncturing and shortening of a single mother code, namely, theIEEE 802.3ca LDPC mother code, incorporated herein by reference in itsentirety. Burst termination involves possibly using a differentpuncturing and minimum shortening for the last codeword in a burst inorder to improve efficiency while still achieving bit-error rate (BER)performance equal to or better than the baseline LDPC code. Thoseskilled in the art will understand that different FEC codes will be moreor less appropriate for use in transmitting signals over the fiber plant104 depending on the current channel characteristics, trading offthroughput vs. BER performance.

In certain embodiments, the OLT 102 may transmit unicast PLOAMdburst-profile messages to different ONUs 106 that specify differentburst profiles for use by the ONUs 106 in their upstream burst-modetransmissions, where each burst profile is associated with an identifiedFEC code. Each ONU 106 that receives a unicast PLOAMd burst-profilemessage, processes the message to determine whether the ONU 106 supportsthe specified burst profile with the identified FEC code and transmits aPLOAMu acknowledgement (ACK) message back to the OLT 102 indicating theresult of that processing. If the PLOAMu ACK message indicates that theONU 106 supports the specified burst profile with the identified FECcode, then the OLT 102 may subsequently transmit a unicast PLOAMdburst-grant message to that ONU 106 indicating the time period for theONU 106 to transmit upstream data using that burst profile and FEC codeas indicated by a burst-profile index contained in the PLOAMdburst-grant message.

Note that, in some implementations, the OLT 102 maintains two differentlists of FEC codes for each ONU 106: a first list of possible FEC codes(i.e., FEC codes that the ONU 106 might support) and a second list ofsupported FEC codes (i.e., FEC codes that the OLT 102 has previouslydetermined are supported by the ONU 106). When a new ONU 106 is added tothe PON network 100, the first list of possible FEC codes for that ONU106 is initiated to include one or more non-default FEC codes, and thesecond list of supported FEC codes for that ONU 106 is initiated toinclude only the default FEC code. As described below in the context ofFIGS. 2 and 3, over time, the OLT 102 may determine whether or not theONU 106 supports one or more of the non-default FEC codes in the firstlist. If the messaging structure subsequently reveals that a particularnon-default FEC code is supported by the ONU 106, then the OLT 102 willremove that non-default FEC code from the first list and add that samenon-default FEC code to the second list. If the messaging structurereveals that the ONU 106 does not support a particular non-default FECcode, then the OLT 102 will remove that non-default FEC code from thefirst list and not add that same non-default FEC code to the secondlist.

FIG. 2 is a flow diagram of the processing implemented by the OLT 102 ofFIG. 1 to determine whether a particular ONUk 106 supports a specifiedburst profile have an identified non-default FEC code j, according tocertain embodiments of the disclosure. FIG. 3 is a flow diagram of theprocessing implemented at the ONUk 106 of FIG. 2, in response to thereceipt of the PLOAMd burst-profile message from the OLT 102, accordingto certain embodiments of this disclosure.

In Step 202 of FIG. 2, the OLT 102 sends to the ONUk 106 a unicastPLOAMd burst-profile message specifying a particular burst profile andidentifying a particular FEC code j, where the FEC code j may be thedefault FEC code or a non-default FEC code. In certain embodiments, theunicast PLOAMd burst-profile message may contain (i) a two-bitburst-profile index in Octet 5 that identifies one of four differentpossible burst profiles and (ii) a multi-bit FEC-code index thatidentifies the particular FEC code j.

In certain embodiments, the two-bit burst-profile index value 0x00 isassigned to a specified burst profile having the default FEC code. Eachother burst-profile index value (i.e., 0x01, 0x02, and 0x03) may beassigned to a different specified burst profile having either (i) thedefault FEC code or (ii) one of the non-default FEC codes.

In certain embodiments, the FEC-code index may have up to six bits inOctet 6, where the default FEC code is indicated by an FEC-code indexvalue having all 0s and the non-default FEC codes are indicated by otherFEC-code index values. For example, if the FEC-code index has four bitsin Octet 6, then there may be up to 16 different FEC codes: the defaultFEC code and up to 15 different non-default FEC codes.

Referring now to Step 302 of FIG. 3, the ONUk 106 receives the unicastPLOAMd burst-profile message with the specified burst profile and theidentified FEC code j transmitted by the OLT 102 in Step 202 of FIG. 2.In Step 304, the ONUk 106 determines whether the ONUk 106 supports theidentified FEC code j. If not, then, in Step 306, the ONUk 106 transmitsa “negative” PLOAMu ACK message to the OLT 102 indicating that theidentified FEC code j is not supported. Otherwise, if the ONUk 106supports the identified FEC code j, then, in Step 308, the ONUk 106determines whether the ONUk 106 supports the other features of thespecified burst profile. If so, then, in Step 310, the ONUk 106transmits a positive PLOAMu ACK message to the OLT 102 indicating thatthe ONUk 106 supports the specified burst profile with the identifiedFEC code j. Otherwise, in Step 312, the ONUk 106 transmits a negativePLOAMu ACK message indicating the reason for not supporting thespecified burst profile (i.e., a reason other than the ONUk 106 notsupporting the identified FEC code j).

In certain embodiments, the PLOAMu ACK message may include an octetnamed Completion_code that has the following seven defined values:

-   -   0x00: OK,    -   0x01: No message to send,    -   0x02: Busy, preparing a response,    -   0x03: Unknown message type,    -   0x04: Parameter error,    -   0x05: Processing error, and    -   0x06: FEC code not supported,        where the Completion_code value 0x06 indicates that the ONU 106        does not support the FEC code j identified in Octet 6 of the        PLOAMd burst-profile message. The other possible values of the        Completion_code octet may be available. Thus, in these        embodiments, in Step 306, the ONUk 106 transmits a negative        PLOAMu ACK message having the Completion_code value 0x06; in        Step 310, the ONUk 106 transmits a positive PLOAMu ACK message        having the Completion_code value 0x00; and, in Step 312, the        ONUk 106 transmits a negative PLOAMu ACK message having one of        the other Completion_code value indicating the particular reason        for not supporting the specified burst profile.

In other possible embodiments, the Completion_code octet might not havethe value 0x06 defined as listed above. In that case, in Step 306, theONUk 106 may transmit a negative PLOAMu ACK message having one of theother Completion_code values, such as 0x04.

Referring again to FIG. 2, in Step 204, the OLT 102 receives the PLOAMuACK message transmitted from the ONUk 106 in one of Steps 306, 310, and312 of FIG. 3. In Step 206, the OLT 102 determines whether the PLOAMuACK message is a positive ACK message, meaning that the ONUk 106supports the specified burst profile with the identified FEC code j. Ifso, then, in Step 208, the OLT 102 updates the first and second lists ofFEC codes for the ONUk 106 as appropriate. In particular, if theidentified FEC code j is a non-default FEC code that is in the firstlist of possible FEC codes for ONUk 106, then the OLT 102 removes thatnon-default FEC code j from the first list and adds that non-default FECcode j to the second list of supported FEC codes for ONUk 106. Notethat, if the identified FEC code j is the default FEC code or anon-default FEC code that is already in the second list, then the OLT102 does nothing in Step 208.

Referring again to Step 206, if the OLT 102 determines that the PLOAMuACK message is a negative ACK message, then, in Step 210, the OLT 102determines whether the PLOAMu ACK message indicates that the ONUk 106supports the identified FEC code j. If not, then, in Step 212, the OLT102 updates the first list of possible FEC codes for the ONUk 106 asappropriate. In particular, if the identified FEC code j is anon-default FEC code that is in the first list of possible FEC codes forONUk 106, then the OLT 102 removes that non-default FEC code j from thefirst list, but does not update the second list of supported FEC codesfor ONUk 106. Note that, if the identified FEC code j is the default FECcode or a non-default FEC code that is not in the first list, then theOLT 102 does nothing in Step 212.

If, in Step 210, the OLT 102 determines that the ONUk 106 fails tosupport the specified burst profile for some reason other than notsupporting the identified FEC code j, then the processing of FIG. 2 endsat Step 214 with the OLT 102 updating neither the first list nor thesecond list.

Note that, if the OLT 102 fails to receive a PLOAMu ACK message from theONUk 106 within a specified duration of transmitting the PLOAMdburst-profile message in Step 202, the OLT 102 responds in some otherappropriate manner not related to whether or not the ONUk 106 supportsthe specified burst profile and the identified FEC code j.

FIGS. 4 and 5 schematically illustrate examples of the OLT 102 and ONUs106, respectively, of FIG. 1. Each OLT 102 and ONU 106 has an opticaltransmitter 402/502 and an optical receiver 404/504 that are connectedvia an optical fiber interface 406/506, e.g., a conventional opticalfiber port, to the optical fiber plant 104 of the PON 100 of FIG. 1. Inthe ONU 106 of FIG. 5, the optical transmitter 502 transmits opticalsignals over the fiber plant 104 upstream to the OLT 102, and theoptical receiver 504 receives optical signals via the fiber plant 104downstream from the OLT 102. In the OLT 102 of FIG. 4, the opticaltransmitter 402 transmits optical signals over the fiber plant 104downstream to the ONUs 106, and the optical receiver 404 receivesoptical signals via the fiber plant 104 upstream from the ONUs 106. Invarious embodiments, the optical transmitters 402/502 and opticalreceivers 404/504 may include various conventional hardware forprocessing optical signals, e.g., in conventional PON or other opticalnetworks. In addition, each of the OLT 102 and the ONUs 106 has anelectronic controller 408/508 configured to control data communicationsand the various message transmission and processing features of theoptical transmitter 402/502 and optical receiver 404/504 therein. Forexample, the electronic controllers 408/508 typically support digitalmessage processing to support various ones of the steps of the methodsillustrated in FIGS. 2 and 3.

In certain embodiments, the present disclosure is an apparatuscomprising an optical network unit (ONU) comprising a receiver and atransmitter to optically communicate with an optical line terminal (OLT)of a passive optical network. The ONU is configured to send anacknowledgment message to the OLT in response to receiving a burstprofile message unicast by the OLT such that the acknowledgement messageindicates unsupported forward error correction (FEC) code in response tothe burst profile message identifying an FEC code for encoding upstreamburst transmission and the ONU not supporting the FEC code for encodingupstream burst transmission to the OLT.

In at least some of the above embodiments, the burst profile message isa downstream physical layer operations, administration and maintenance(PLOAM) message, and the acknowledgement message is an upstream PLOAMmessage.

In at least some of the above embodiments, the ONU is configured to usea predefined set of six or less bits of received burst profile messagesto determine FEC codes for upstream burst transmission identifiedtherein.

In at least some of the above embodiments, the ONU is configured toindicate a not supported first FEC code for upstream burst transmissionto the OLT by setting a completion code value in a PLOAM acknowledgementmessage.

In at least some of the above embodiments, the ONU is configured to usethe same completion code value to indicate in a PLOAM acknowledgementmessage that a second FEC code is not supported for encoding upstreamburst transmission to the OLT.

In at least some of the above embodiments, the same completion codevalue indicates only that the identified FEC code is not supported bythe ONU.

In at least some of the above embodiments, the ONU is configured totransmit the acknowledgment message with an indication of supported FECcode in response to the ONU supporting the identified FEC code forencoding upstream transmission to the OLT.

In at least some of the above embodiments, the ONU is enabled to send aburst transmission to the OLT using a particular FEC code in response tothe OLT transmitting a message to the ONU requesting that the ONU usethe particular FEC code and the ONU having transmitted theacknowledgement message with the indication supported FEC code thereinin response to the received burst profile message identifying theparticular FEC code.

In at least some of the above embodiments, the ONU supports at least twodifferent FEC codes for upstream transmission to the OLT.

In at least some of the above embodiments, the two different FEC codesare both obtainable by puncturing and/or shortening a mother code basedon an LDPC type of FEC.

In certain embodiments, the present disclosure is an apparatuscomprising an OLT having a transmitter and receiver to opticallycommunicate with ONUs of a PON, the OLT being configured to unicast aburst profile message to one of the ONUs such that the burst profilemessage identifies one FEC code for encoding upstream bursttransmission, the OLT being configured to identify the one FEC code asnot supported by the one of the ONUs in response to receiving anacknowledgement message responsive to the burst profile message, theacknowledgement message indicating unsupported FEC code for encodingupstream burst transmission.

In at least some of the above embodiments, the burst-profile message isdownstream physical layer operations, administration and maintenance(PLOAM) message, and the acknowledgement message is an upstream PLOAMmessage.

In at least some of the above embodiments, the OLT is configured to usea predefined set of six or less bits of burst profile messages toidentify FEC codes for encoding upstream burst transmissions.

In at least some of the above embodiments, the OLT is configured toidentify the one FEC code as supported for encoding upstream bursttransmission by the one of the ONUs in response to receiving responsiveto the burst-profile message an acknowledgement message with anindication of supported FEC code for encoding upstream bursttransmission.

In at least some of the above embodiments, the OLT is configured to beenabled to request a burst from the one of the ONUs using the one FECcode in response to receipt of the acknowledgement message to the burstprofile message indicating a supported FEC code for encoding upstreamburst transmission.

In at least some of the above embodiments, the OLT is configured to usea value of a completion code in an upstream PLOAM acknowledgementmessage to determine that an FEC code is unsupported by an ONU forencoding upstream burst transmission.

In at least some of the above embodiments, the OLT is configured toidentify multiple FEC codes as being not supported for upstreamtransmission by the same value of the completion code.

In at least some of the above embodiments, the same completion codevalue indicates only that the one FEC code is not supported by the ONU.

Embodiments of the disclosure may be implemented as (analog, digital, ora hybrid of both analog and digital) circuit-based processes, includingpossible implementation as a single integrated circuit (such as an ASICor an FPGA), a multi-chip module, a single card, or a multi-card circuitpack. As would be apparent to one skilled in the art, various functionsof circuit elements may also be implemented as processing blocks in asoftware program. Such software may be employed in, for example, adigital signal processor, micro-controller, general-purpose computer, orother processor.

As will be appreciated by one of ordinary skill in the art, the presentdisclosure may be embodied as an apparatus (including, for example, asystem, a machine, a device, a computer program product, and/or thelike), as a method (including, for example, a business process, acomputer-implemented process, and/or the like), or as any combination ofthe foregoing. Accordingly, embodiments of the present disclosure maytake the form of an entirely software-based embodiment (includingfirmware, resident software, micro-code, and the like), an entirelyhardware embodiment, or an embodiment combining software and hardwareaspects that may generally be referred to herein as a “system.”

Embodiments of the disclosure can be manifest in the form of methods andapparatuses for practicing those methods. Embodiments of the disclosurecan also be manifest in the form of program code embodied in tangiblemedia, such as magnetic recording media, optical recording media, solidstate memory, floppy diskettes, CD-ROMs, hard drives, or any othernon-transitory machine-readable storage medium, wherein, when theprogram code is loaded into and executed by a machine, such as acomputer, the machine becomes an apparatus for practicing thedisclosure. Embodiments of the disclosure can also be manifest in theform of program code, for example, stored in a non-transitorymachine-readable storage medium including being loaded into and/orexecuted by a machine, wherein, when the program code is loaded into andexecuted by a machine, such as a computer, the machine becomes anapparatus for practicing the disclosure. When implemented on ageneral-purpose processor, the program code segments combine with theprocessor to provide a unique device that operates analogously tospecific logic circuits.

Any suitable processor-usable/readable or computer-usable/readablestorage medium may be utilized. The storage medium may be (withoutlimitation) an electronic, magnetic, optical, electromagnetic, infrared,or semiconductor system, apparatus, or device. A more-specific,non-exhaustive list of possible storage media include a magnetic tape, aportable computer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory(EPROM) or Flash memory, a portable compact disc read-only memory(CD-ROM), an optical storage device, and a magnetic storage device. Notethat the storage medium could even be paper or another suitable mediumupon which the program is printed, since the program can beelectronically captured via, for instance, optical scanning of theprinting, then compiled, interpreted, or otherwise processed in asuitable manner including but not limited to optical characterrecognition, if necessary, and then stored in a processor or computermemory. In the context of this disclosure, a suitable storage medium maybe any medium that can contain or store a program for use by or inconnection with an instruction execution system, apparatus, or device.

The functions of the various elements shown in the figures, includingany functional blocks labeled as “processors,” may be provided throughthe use of dedicated hardware as well as hardware capable of executingsoftware in association with appropriate software. When provided by aprocessor, the functions may be provided by a single dedicatedprocessor, by a single shared processor, or by a plurality of individualprocessors, some of which may be shared. Moreover, explicit use of theterm “processor” or “controller” should not be construed to referexclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, network processor, application specific integrated circuit(ASIC), field programmable gate array (FPGA), read only memory (ROM) forstoring software, random access memory (RAM), and non-volatile storage.Other hardware, conventional and/or custom, may also be included.Similarly, any switches shown in the figures are conceptual only. Theirfunction may be carried out through the operation of program logic,through dedicated logic, through the interaction of program control anddedicated logic, or even manually, the particular technique beingselectable by the implementer as more specifically understood from thecontext.

It should be appreciated by those of ordinary skill in the art that anyblock diagrams herein represent conceptual views of illustrativecircuitry embodying the principles of the disclosure. Similarly, it willbe appreciated that any flow charts, flow diagrams, state transitiondiagrams, pseudo code, and the like represent various processes whichmay be substantially represented in computer readable medium and soexecuted by a computer or processor, whether or not such computer orprocessor is explicitly shown.

Unless explicitly stated otherwise, each numerical value and rangeshould be interpreted as being approximate as if the word “about” or“approximately” preceded the value or range.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, percent, ratio,reaction conditions, and so forth used in the specification and claimsare to be understood as being modified in all instances by the term“about,” whether or not the term “about” is present. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thespecification and claims are approximations that may vary depending uponthe desired properties sought to be obtained by the present disclosure.At the very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques. Notwithstanding that the numerical ranges and parameterssetting forth the broad scope of the disclosure are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements.

It will be further understood that various changes in the details,materials, and arrangements of the parts which have been described andillustrated in order to explain embodiments of this disclosure may bemade by those skilled in the art without departing from embodiments ofthe disclosure encompassed by the following claims.

In this specification including any claims, the term “each” may be usedto refer to one or more specified characteristics of a plurality ofpreviously recited elements or steps. When used with the open-ended term“comprising,” the recitation of the term “each” does not excludeadditional, unrecited elements or steps. Thus, it will be understoodthat an apparatus may have additional, unrecited elements and a methodmay have additional, unrecited steps, where the additional, unrecitedelements or steps do not have the one or more specified characteristics.

The use of figure numbers and/or figure reference labels in the claimsis intended to identify one or more possible embodiments of the claimedsubject matter in order to facilitate the interpretation of the claims.Such use is not to be construed as necessarily limiting the scope ofthose claims to the embodiments shown in the corresponding figures.

It should be understood that the steps of the exemplary methods setforth herein are not necessarily required to be performed in the orderdescribed, and the order of the steps of such methods should beunderstood to be merely exemplary. Likewise, additional steps may beincluded in such methods, and certain steps may be omitted or combined,in methods consistent with various embodiments of the disclosure.

Although the elements in the following method claims, if any, arerecited in a particular sequence with corresponding labeling, unless theclaim recitations otherwise imply a particular sequence for implementingsome or all of those elements, those elements are not necessarilyintended to be limited to being implemented in that particular sequence.

All documents mentioned herein are hereby incorporated by reference intheir entirety or alternatively to provide the disclosure for which theywere specifically relied upon.

Reference herein to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment can be included in at least one embodiment of thedisclosure. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment, nor are separate or alternative embodiments necessarilymutually exclusive of other embodiments. The same applies to the term“implementation.”

The embodiments covered by the claims in this application are limited toembodiments that (1) are enabled by this specification and (2)correspond to statutory subject matter. Non-enabled embodiments andembodiments that correspond to non-statutory subject matter areexplicitly disclaimed even if they fall within the scope of the claims.

As used herein and in the claims, the term “provide” with respect to anapparatus or with respect to a system, device, or component encompassesdesigning or fabricating the apparatus, system, device, or component;causing the apparatus, system, device, or component to be designed orfabricated; and/or obtaining the apparatus, system, device, or componentby purchase, lease, rental, or other contractual arrangement.

Unless otherwise specified herein, the use of the ordinal adjectives“first,” “second,” “third,” etc., to refer to an object of a pluralityof like objects merely indicates that different instances of such likeobjects are being referred to, and is not intended to imply that thelike objects so referred-to have to be in a corresponding order orsequence, either temporally, spatially, in ranking, or in any othermanner.

1. An apparatus, comprising: an optical network unit (ONU) comprising areceiver and a transmitter to optically communicate with an optical lineterminal (OLT) of a passive optical network; and wherein the ONU isconfigured to send an acknowledgement message to the OLT in response toreceiving a management message unicast by the OLT such that theacknowledgement message explicitly indicates unsupported feature inresponse to the management message identifying an-the feature as aparticular (forward error correction (FEC) code for encoding upstreamburst transmission and the ONU not supporting the particular FEC codefor encoding upstream burst transmission to the OLT.
 2. The apparatus ofclaim 1, wherein: the management message is a downstream physical layeroperations, administration and maintenance message; and theacknowledgement message is an upstream physical layer operations,administration and maintenance message.
 3. (canceled)
 4. The apparatusof claim 1, wherein the ONU is configured to indicate a not supportedfirst FEC code for upstream burst transmission to the OLT by setting acompletion code value in the acknowledgement message.
 5. The apparatusof claim 4, wherein the ONU is configured to use the same completioncode value to indicate in another acknowledgement message that a secondFEC code is not supported for encoding upstream burst transmission tothe OLT.
 6. The apparatus of claim 4, wherein the same completion codevalue indicates only that the particular FEC code is not supported bythe ONU.
 7. The apparatus of claim 1, wherein the ONU is configured totransmit an acknowledgement message with an indication of the featurebeing supported in response to the received management messageidentifying the feature as the particular FEC code and for encodingupstream burst transmission and the ONU supporting the particular FECcode for encoding upstream transmission to the OLT.
 8. The apparatus ofclaim 7, wherein the ONU is enabled to send a burst transmission to theOLT using the particular FEC code in response to the OLT transmitting amessage to the ONU requesting that the ONU use the particular FEC codeand the ONU having transmitted the acknowledgement message with anindication of the feature being supported in response to a-the receivedmanagement message identifying the feature as the particular FEC codefor encoding upstream burst transmission.
 9. The apparatus of claim 1,wherein the ONU supports at least two different FEC codes for upstreamtransmission to the OLT.
 10. The apparatus of claim 9, wherein the twodifferent FEC codes are both obtainable by puncturing and/or shorteninga mother code based on an LDPC type of FEC.
 11. An apparatus,comprising: an OLT having a transmitter and receiver to opticallycommunicate with ONUs of a PON, the OLT being configured to unicast amanagement message to one of the ONUs such that the management messageidentifies a feature for encoding upstream burst transmission, thefeature being one FEC code, the OLT being configured to identify the oneFEC code as not supported by the one of the ONUs in response toreceiving an acknowledgement message responsive to the managementmessage, the acknowledgement message explicitly indicating the featurefor encoding upstream burst transmission is unsupported.
 12. Theapparatus of claim 11, wherein: the management message is downstreamphysical layer operations, administration and maintenance message; andthe acknowledgement message is an upstream physical layer operations,administration and maintenance message.
 13. The apparatus of claim 11,wherein the OLT is configured to use a predefined set of six or lessbits of management messages to identify FEC codes for encoding upstreamburst transmissions.
 14. The apparatus of claim 11, wherein the OLT isconfigured to identify another FEC code as supported for encodingupstream burst transmission by the one of the ONUs in response toreceiving responsive to the management message another acknowledgementmessage with an indication of supported feature for encoding upstreamburst transmission.
 15. (canceled)
 16. The apparatus of claim 11,wherein the OLT is configured to use a value of a completion code in theacknowledgement message to determine that the FEC code is unsupported bythe ONU for encoding upstream burst transmission.
 17. The apparatus ofclaim 16, wherein the OLT is configured to identify multiple FEC codesas being not supported for upstream transmission by the same value ofthe completion code.
 18. The apparatus of claim 16, wherein the samecompletion code value indicates only that the one FEC code is notsupported by the ONU. 19-20. (canceled)
 21. The apparatus of claim 1,wherein: the management message identifies only a single FEC code forencoding upstream burst transmission; and the acknowledgement messageexplicitly indicates that the ONU does not support the identified singleFEC code.
 22. The apparatus of claim 21, wherein: the management messagecontains a multi-bit FEC-code index identifying the single FEC code; andthe acknowledgement message contains a completion code value explicitlyindicating that the ONU does not support the identified single FEC code.23. The apparatus of claim 11, wherein: the management messageidentifies only a single FEC code for encoding upstream bursttransmission; and the acknowledgement message explicitly indicates thatthe ONU does not support the identified single FEC code.
 24. (canceled)25. An apparatus, comprising: an optical network unit (ONU) comprising areceiver and a transmitter to optically communicate with an optical lineterminal (OLT) of a passive optical network; and wherein the ONU isconfigured to send an acknowledgement message to the OLT in response toreceiving a management message unicast by the OLT such that theacknowledgement message explicitly indicates unsupported forward errorcorrection (FEC) code in response to the management message identifyingan FEC code for encoding upstream burst transmission and the ONU notsupporting the FEC code for encoding upstream burst transmission to theOLT.
 26. The apparatus of claim 25, wherein: the management message is adownstream physical layer operations, administration and maintenancemessage; and the acknowledgement message is an upstream physical layeroperations, administration and maintenance message.